1. Field of the Invention
The present invention relates to a ballpoint pen oil-based ink composition, which is suitably used as a ballpoint pen oil-based ink, to prevent the written letters and the like from being blurred at the start of writing, provide soft writing and smooth feeling on writing, and allow the ink to quickly penetrate into the surface of a material written down on, and exhibits excellent drying property at the pen tip.
2. Background Art
Oil-based ballpoint pens are heretofore liable to suffer from a problem such that due to thickening of ink at the distal end of the ball chip resulting from evaporation of the solvent in ink, the ink is not easily ejected at the start of writing, or writing with sufficiently high density cannot be obtained until the ball starts fully rotating. This blur phenomenon greatly depends on the environmental conditions and often occurs under low-temperature or high-temperature conditions to cause unpleasantness. In the case of using a solvent having high volatility, this phenomenon occurs outstandingly and becomes a serious problem.
In order to solve this problem, various studies have been heretofore made. For example, Japanese Examined Patent Publication (Kokoku) No. 61-52872 discloses a technique of keeping the fluidity of ink by adding a specific nonionic surfactant, Japanese Examined Patent Publication (Kokoku) No. 57-38629 discloses a technique of using a high boiling point aromatic hydrocarbon as a solvent to prevent the ink from drying or absorbing moisture and thereby deteriorating, Japanese Unexamined Patent Publication (Kokai) No. 3-28279discloses a technique of keeping the fluidity of ink by adding a phosphoric acid ester, and Japanese unexamined Patent Publication No. 6-247093 discloses a technique of using a nonvolatile solvent to prevent the ink from completely drying out.
Japanese Unexamined Patent Publication (Kokai) No. 11-158421 discloses a technique where a salt of a basic dye with a phosphoric acid ester is blended to prevent the dye from crystallizing at the pen tip, as a result, the ink can be prevented from drying to solidify and can be obtained in the grease to paste state at the pen tip, so that the fluidity of ink can be maintained and writing can smoothly start, thereby overcoming the problem of blur. Also, Japanese Unexamined Patent Publication (Kokai) No. 11-21495 discloses a technique of neutralizing an acidic polyoxyethylene alkyl ether phosphate with a predetermined alkylalkanolamine or morpholine, where the same effect as above is obtained. However, the amine substance used here has strong odor and high reactivity and therefore, the latitude in selecting the solvent, dye and the like is liable to be narrow.
Although there arises no problem in the case of solvents having a vapor pressure of less than 0.01 mmHg used in conventional oily-based ballpoint pens, the solvent for use in the present invention has a high vapor pressure and when an ink agglomerate solidifies in the periphery of ball, an extremely large writing load is necessary on starting the writing by moving the ball.
The object of the present invention is to provide a ballpoint pen oil-based ink composition, which, unlike conventional techniques, renders the ball surface to be hardly wetted upon drying of the ink, facilitates the removal of dry agglomerate from the periphery of ball, prevents the blur of written letters and the like at the start of writing, and enables smooth start of writing. The object of the present invention includes providing an oil-based ballpoint pen using said oil-based ink composition.
In order to attain these objects, it has been found that the above-described problems can be solved by the ballpoint pen oil-based ink composition of the present invention, which is characterized by the following features. The present invention has been accomplished based on this finding,
(1) A ballpoint pen oil-based ink composition, comprising a colorant, an oil-based solvent, at least one phosphoric acid ester having an acid value of 90 to 600, and at least one weakly cationic component selected from the group consisting of:
a) imidazoline-type activator,
b) polyoxyethylene alkylamine,
c) polyoxyethylene alkylamide, and
d) alkylalkanolamide.
(2) The ballpoint pen oil-based ink composition as in (1), wherein the polyoxyethylene alkylamine and polyoxyethylene alkylamide each has a polyoxyethylene addition molar number of 2 to 50 and the alkyl group in the amine or amide is derived from an acid or alcohol having from 10 to 30 carbon atoms.
(3) The ballpoint pen oil-based ink composition as in (1) and (2), wherein said solvent comprises at least a solvent selected from the group consisting of alcohols, polyhydric alcohols and glycol ethers each having a vapor pressure at 25xc2x0 C. of 0.001 mmHg or more.
(4) The ballpoint pen oil-based ink composition as in (1) to (3), wherein said solvent comprises, as a main solvent, at least a solvent selected from the group consisting of alcohols, polyhydric alcohols and glycol ethers each having a vapor pressure at 25xc2x0 C. of 0.01 mmHg or more.
(5) A ballpoint pen comprising an ink holder, the ballpoint pen oil-based ink composition as in (1) to (4) in said ink holder, and an ballpoint pen tip provided at an end of the ink holder.
(6) The ballpoint pen as in (5), further comprising an ink follower provided in said ink holder at another end of the ink composition opposite to the ballpoint pen tip.
(7) The ballpoint pen as in (5) or (6), wherein said ballpoint pen tip comprises a ceramic micro ball.